Midi Vertical Gel Electrophoresis System

What is the Midi Vertical Gel Electrophoresis System?

A vertical unit for 16 x 16 cm gels that gives a separation path about twice as long as a mini gel. It is chosen for complex protein samples and medium-throughput work needing better band resolution.

Overview

The midi system uses glass plates of about 18 x 16 cm that cast gels around 16 x 14 cm, doubling the migration distance of a mini gel. The added length separates proteins that differ by only a few percent in molecular weight and provides sharper resolution for gradient gels, post-translational modification studies and lysate fingerprints. Combs of 15, 20 or 26 teeth and thicknesses of 0.75 to 1.5 mm are common. Buffer volume is typically 1.5–3 L, and runs at 150–250 V last 2–4 hours, so a cooling plate or circulating water jacket is usually integrated to prevent smiling bands. One or two gels can be mounted in the same tank, and a multi-gel caster prepares several slabs at once. The midi format is a practical step between routine mini checks and the demands of full large-format proteomics.

How does it work?

In a vertical system a polyacrylamide gel is cast between two glass plates separated by spacers and mounted so that its top edge dips into an upper buffer chamber and its bottom edge into a lower one. Voltage across the two chambers drives charged molecules down through the gel. Polyacrylamide forms a tighter and more uniform mesh than agarose, and its pore size is set by total acrylamide percentage and crosslinker ratio, so proteins or fragments differing by a few kilodaltons or a single nucleotide can be resolved. In discontinuous SDS-PAGE, a stacking gel concentrates samples into a sharp band before they enter the resolving gel. Key parts include the plates, spacers, combs, clamps, gaskets, buffer chambers and a cooling core or plate that removes Joule heat.

What are the key features?

• Plates of about 18 x 16 cm cast gels with roughly double the migration distance of a mini gel
• Integrated cooling plate or water jacket reduces smiling and heat-related band distortion
• Comb options of 15, 20 and 26 teeth at 0.75, 1.0 and 1.5 mm thickness
• Accepts one or two gels in the same tank with a dummy plate for single-gel runs
• Multi-gel caster prepares up to six slabs of uniform height in one pour
• Safety lid with interlock and shrouded leads supports long unattended runs

What are the technical specifications?

A typical midi vertical gel electrophoresis system configuration offers gel size (W x L) of approx. 16 x 14 cm, gel thickness options of 0.75, 1.0, 1.5 mm, number of gels per run of 1–2, wells per comb of 15, 20, 26, buffer volume of approx. 1.5–3 L and maximum voltage of 500 V DC. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Midi Vertical Gel Electrophoresis System is used in complex lysate separation, gradient gel protein profiling, post-translational modification studies and medium-throughput proteomics. Across the wider Vertical Electrophoresis class, laboratories also deploy it for SDS-PAGE protein separation, native PAGE and activity gels and two-dimensional electrophoresis.

Which standards and certifications apply?

Relevant standards and methods include IEC 61010-1, IEC 61326-1, Ph. Eur. 2.2.31, USP <1053> and ISO 17025. Certification candidates for this model are CE, ISO 9001 manufacturing and RoHS; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Assemble plates on a clean, flat surface and check gaskets and spacers for damage before each cast, since leaks ruin gels and contaminate the lower chamber. Acrylamide monomer is neurotoxic, so use gloves and cured gels or pre-cast products where possible. Use fresh APS and TEMED for reproducible polymerisation. Keep buffer chambers filled to the marked level and fit the cooling core for long runs. Clean glass plates with non-abrasive detergent and never use razor blades for separation. Electrical safety follows IEC 61010-1, with interlocked lids and insulated leads. Keep records of gel percentage, buffer batch and run conditions, and verify performance with molecular weight markers.

How do I select the right Midi Vertical Gel Electrophoresis System?

Select a midi system when mini gels cannot resolve closely sized proteins or complex lysates. It uses more buffer and run time and often needs cooling. Specify gel size, thickness, well count, maximum voltage, cooling option and whether a multi-gel caster is required.

How does it compare with other Vertical Electrophoresis variants?

Decide the gel format from the application. Mini gels of about 8 x 7 cm are quick and economical for routine protein checks and western blot preparation. Midi and large-format gels give longer separation paths for complex samples, and 20 x 20 cm plates are standard for two-dimensional electrophoresis. Sequencing apparatus with long thin plates suits nucleic acid work at single-base resolution. Consider throughput, whether multiple gels must be run and cast together, and whether cooling is needed for long high-voltage runs. Check gel thickness options from 0.75 to 1.5 mm, comb well counts, compatibility with pre-cast gels, and plate and spacer quality, because chipped glass causes leaks. Match the power supply to voltage and current needs, especially for multi-gel runs.